Copyright Goodheart-Willcox Co., Inc. 276 AutoCAD and Its Applications—Advanced history is recorded, as discussed in Chapter 8. The primitive subobjects can be edited. See Figure 11-9. Once selected, the primitive subobjects can be modifi ed or deleted as needed from the composite solid. Figure 11-10 illustrates the difference between a composite solid model, the solid primitives used to construct it, and an individual subobject of one of the primitives. Subobjects can be easily edited using grips, which provide an intuitive and fl ex- ible method of solid model design. For example, suppose you need to rotate a face subobject in the current XY plane. You can select the subobject, pick its base grip, and then cycle through the editing functions to the rotate function. You can also use the ROTATE command on the selected subobject. To select a subobject, press the [Ctrl] key and pick the subobject. You can select multiple subobjects and subobjects on multiple objects. To select a subobject that is hidden in the current view, fi rst display the model as a wireframe. After creating a selection set, select a grip and edit the subobject as needed. Multiple objects can be Grip to move A B Figure 11-7. Surfaces extruded from an arc, line, and polyline. Notice the grips. Figure 11-8. A—Grips can be used to modify the path on this swept surface. B—The swept surface after grip editing.